P-51C at ~70% scale as ultralight?

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J.L. Frusha

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I do not understand the switch from areas to volume. That's not some direct comparison. It's going from square ft to cubic feet, without any point of ref. How can the horizontal tail have insufficient volume, aside from being a flimsy, ineffective sheet...?

HOWEVER, the entire assy IS 3 dimensional. I DID see a comparison of the horizontal stabilizer area to wing area (~15%-35%), so took that and bumped up the verticalal stab by the same amount as well...

I do not know how to run the calculations for everything, but I can change what I understand...

However, it IS bringing the Horiz Stab closer to the TE of the wing. ince it is still almost directly inline with the prop and above the wing, I don't 'think' it will be an issue, especially at the lower speeds of an ultralight.

Best Guess #2...

 

pictsidhe

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Fowler flaps have a more pitching moment change than plain or split flaps. Their motion is also fairly complex, requiring a track. You need to be thinking about how you get into the cockpit. It will involve treading on the wing. One reason I am using split flaps. I doubt that there is a simple and light way to build foot proof fowler flaps.
Slotted flaps of handley-page or Blackburn type with their simple hinge might be worth a look. The NACA slotted flaps have a complex path again.
 

Tiger Tim

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I do not understand the switch from areas to volume. That's not some direct comparison. It's going from square ft to cubic feet, without any point of ref. How can the horizontal tail have insufficient volume, aside from being a flimsy, ineffective sheet...?
“Volume” is probably a poor word to describe it but the term is standard so we’re stuck with it. “Effectiveness” better describes it. I used to know how to do the math on this from free flight model airplane building but the “tail volume” takes into account the surface area of the tail and the moment arm that tail is mounted on, then somewhere in the equation accounts for wing area(?) so that the number you get is independent from the size of the airplane.

In short, it helps in designing a plane with a short fuselage and big stabilizer to be as stable as one with a long fuselage and small stabilizer.
 

BJC

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“Volume” is probably a poor word to describe it but the term is standard so we’re stuck with it. “Effectiveness” better describes it. I used to know how to do the math on this from free flight model airplane building but the “tail volume” takes into account the surface area of the tail and the moment arm that tail is mounted on, then somewhere in the equation accounts for wing area(?) so that the number you get is independent from the size of the airplane.

In short, it helps in designing a plane with a short fuselage and big stabilizer to be as stable as one with a long fuselage and small stabilizer.
TT describes it well.

As to the term “volume”: Because the stabilizing surface area is multiplied by the length of the arm that the stabilizing surface acts through, the resulting units are length to the third power, which commonly is used to indicate volume. That result is divided by another length to the third power term to arrive at what usually is called (by mathematicians) a dimensionless coefficient. Note, however, that coefficients do have dimensions; in this case, length cubed per length cubed.

Note, also, that the geometry and aerodynamics of the fuselage play a role, but may not be accounted for in a simple calculation of “tail volume coefficient.”. Consider, for example, a J-3 aft fuselage contribution to yaw stability verses a Kolb aft fuselage contribution.


BJC
 

J.L. Frusha

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Fowler flaps have a more pitching moment change than plain or split flaps. Their motion is also fairly complex, requiring a track. You need to be thinking about how you get into the cockpit. It will involve treading on the wing. One reason I am using split flaps. I doubt that there is a simple and light way to build foot proof fowler flaps.
Slotted flaps of handley-page or Blackburn type with their simple hinge might be worth a look. The NACA slotted flaps have a complex path again.
The motion can be approximated with a simpler hinge. The complex linkage is generally an attempt to hide the linkage within the wing, instead of having a visible hinge. Like everything, it's a tradeoff... A large, exposed hinge is easier to dammage and creates extra drag. Complex linkage is harder to maintain and weights more.

From the rcgroups fotum, this image shows what I mean...

https://www.rcgroups.com/forums/showthread.php?3035704-Flap-Hinge-Point-Geometry



A good article...

The Flap Over The Flap:
Marty Maisel
Nov. 7, 2010


https://sites.google.com/site/cavalieraircraft/individual-aircraft-pages/split-flaps

By trimming the stop, the TE could even be reflexed, if it might help at cruise.

 

pictsidhe

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The motion can be approximated with a simpler hinge. The complex linkage is generally an attempt to hide the linkage within the wing, instead of having a visible hinge. Like everything, it's a tradeoff... A large, exposed hinge is easier to dammage and creates extra drag. Complex linkage is harder to maintain and weights more.

From the rcgroups fotum, this image shows what I mean...

https://www.rcgroups.com/forums/showthread.php?3035704-Flap-Hinge-Point-Geometry



A good article...

The Flap Over The Flap:
Marty Maisel
Nov. 7, 2010


https://sites.google.com/site/cavalieraircraft/individual-aircraft-pages/split-flaps

By trimming the stop, the TE could even be reflexed, if it might help at cruise.

That's a slotted Blackburn flap, not a Fowler flap. A Fowler flap isn't a Fowler flap without its particular motion. That is needed for good performance at intermediate settings.
 

J.L. Frusha

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That's a slotted Blackburn flap, not a Fowler flap. A Fowler flap isn't a Fowler flap without its particular motion. That is needed for good performance at intermediate settings.
Even AOPA says that the term "Fowler Flap" has been used to describe a broader range of flaps than the strictest application of the term, however, transitioning from no-slot, to extended and lowered position can be done w/o the slides and rollers, which is part of my point. The simpler the mechanism, the easier to inspect and maintain.

Rather than gnit-picking term usage, can you help find a simple linkage that doesn't use complicated tracks and rollers? I don't really mind it having exposed elements.
 

pictsidhe

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Both the handley-page and Blackburn flaps have a simple hinge. HP flaps are closely hinged, Blackburn are your modified 'fowler' flaps. They are fairly simple, which is why I suggested them as possibles. If you want slotted flaps to work well, you either need to spend some time experimenting in a wind tunnel or expensive software, or use the shape derived by someone who already has. To do the latter, knowing the actual name is kinda useful. Fowler flaps are a development of Blackburn flaps.
Google my suggestions and you should find plenty info.
 

cluttonfred

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So your solution to your ultralight design challenge is to adapt a design feature from a Boeing 777? I am beginning to wonder if this thread is serious or just some form of elaborate trolling.
 

Lendo

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I don't know if this helps in any way, I recently got back from Friedrichshafen Airchow Germany and noticed a Carbon P51 at 70%, it was an exact copy of the P51 Airfoil and everything right down to the rivet indentations - I don't know why! It met the Light Sport Category from memory, which they refer to Ultralight in Europe, the dimensions I don't remember and I didn't keep any literature, but I'm sure you could find it on the Internet, this may help with comparisons - just a suggestion.
 

J.L. Frusha

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So your solution to your ultralight design challenge is to adapt a design feature from a Boeing 777? I am beginning to wonder if this thread is serious or just some form of elaborate trolling.

So, you want to go there? Take away EVERY FEATURE this would have in common with a Boeing 777.

What's left? The piston engine, propeller, belly radiator scoop and manual controls... THAT'S IT

No wings, no fuselage, no landing gear, no control surfaces... NOTHING

Who is trolling whom?

I found the simplest link/hinge fowler flap mechanism I have ever seen, and I have gone over thousands of them in the last week, and you want to get picky because it comes off a Boeing 777? What the ever-loving Hell is WRONG with adapting a perfectly functional design that does exactly what it was designed to do, in the easiest, most durable way?
 

pictsidhe

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Sledgehammer to crack an acorn. I am currently spending a lot of time working out how to simplify my design. Simpler is not just easier to build, it is often lighter, roo. Weight is everything on a 103. Weight is everything on a 103. Yes, I said that twice, in case it didn't sink in the first time. I don't need fowler flaps, I just need to hit a CLmax of just over 2. Split flaps will do that, are simple, sturdy and light. Nearly the same CL increment as fowler. Yes, they have a metric **** ton of drag, but I'm ok with that. Full flaps are for two things: To show 103 compliance, and a really short landing. The extra drag is useful for that short landing.
When designing the Zero, Mitsubishi controlled the weight of everything that was more than 0.1% of the aircraft weight. It resulted in a very impressive aircraft. Not a bad target. For a monocoque cantilever 103, it may be necessary, though. You need to save weight everywhere.
 

J.L. Frusha

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Sledgehammer to crack an acorn. I am currently spending a lot of time working out how to simplify my design. Simpler is not just easier to build, it is often lighter, roo. Weight is everything on a 103. Weight is everything on a 103. Yes, I said that twice, in case it didn't sink in the first time. I don't need fowler flaps, I just need to hit a CLmax of just over 2. Split flaps will do that, are simple, sturdy and light. Nearly the same CL increment as fowler. Yes, they have a metric **** ton of drag, but I'm ok with that. Full flaps are for two things: To show 103 compliance, and a really short landing. The extra drag is useful for that short landing.
When designing the Zero, Mitsubishi controlled the weight of everything that was more than 0.1% of the aircraft weight. It resulted in a very impressive aircraft. Not a bad target. For a monocoque cantilever 103, it may be necessary, though. You need to save weight everywhere.

I guess I don't understand...
Doing my own research - Check
Use Fowler Flaps to help get to the FAR 103 stall speed - Check
Use a simple, sturdy, dependable, durable mechanism to do so - Check

Why does using a specific style linkage add up to it NOT being FAR 103? Because it's used on a Jumbo Jet? I never implied I could use THEIR linkage, just the design. Their linkage is specific to the 777 Application, a down-sized, working version for this project makes sense. It is the simplest Fowler Flap Linkage I have found, does not have tracks and rollers, meets all the functional requirements and can do so in a very light package, at this scale. I don't need hydraulics or electric actuators to operate this simple mechanism. Bell-cranks and push-pull rods will suffice to make it work.

It has to be strong enough to support the Fowler Flaps, has to attach securely to the wing to do so, but, Hell, the hinges and linkage for your flaps have to do the same thing.

So... HOW is it using a "Sledgehammer to crack an acorn"...?
 

radfordc

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So your solution to your ultralight design challenge is to adapt a design feature from a Boeing 777? I am beginning to wonder if this thread is serious or just some form of elaborate trolling.
This thread reminds me of Robert X. Cringley (real name Mark Stevens) and his TV show "Plane Crazy". Ostensibly his effort to design and build a plane in 30 days, but actually a way of getting his TV show produced with no meaningful attempt to actually design/build a plane. https://www.nytimes.com/1998/07/22/arts/television-review-the-zen-of-building-a-plane-yourself.html
 

J.L. Frusha

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I've tried to adapt and overcome at every turn, been jumped on for it being too long, then too little wing area, then too small a tailplane, overadjusting, making the necessary changes, found a simple way to use fowler flaps to achieve the stall speed with slightly less wing area than the charts recommend and most of y'all think it's all an elaborate joke?
 
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